Packet Tracer: OSPF, NAT and Routing Troubleshooting 

For huge networks, (like the internet) the protocol that joins huge networks together (such as the service provider networks) is BGP. Inside those service providers, it likely that most of them use an Interior Gateway Protocol (IGP) that is link-state. Their IGP is most likely to be OSPF or IS-IS. EIGRP is an advanced Distance Vector routing protocol, and I see that used occasionally, but rarely as the main IGP. EIGRP converges very fast, as do the link state protocols. Cheers, Keith

Thanks for the feedback, I am glad you liked it. Best wishes, Keith Barker

The null route, is just so the route can get into OSPF (through redistribution). The NAT translations are more specific than a /27 (from the NAT), so the longest route concept takes place. Longest match wins.

An IGP (interior gateway protocol) refers to a routing protocol. Examples of IGPs are RIP, OSPF, EIGRP and IS-IS. An EGP (external gateway protocol) is BGP. Inside a company the choice of which routing protocol is up to that company. RIP is the worst, as it is slow to converge. EIGRP is proprietary, and OSPF is the primary protocol used these days with some IS-IS for service providers (because they want to, not because they have to).

Really appreciate the time you take to make these videos. Im currently a networking student and your videos are a great source of information, keep them coming.

For the service providers, they will likely be using OSPF or IS-IS as their IGP. They also use BGP to connect to other service providers, but they also use BGP for some other creative services (such as MPLS L3 VPNs).

i just couldn't make the nat via ospf work but when i watched this video, i just learned something new and i am glad that it did work! glad i found this video

You can connect large networks together with static routes, it is just a lot of manual work, and it doesn't dynamically adjust to changes (networks coming up or going down). If RIP, OSPF and EIGRP were all using internal routes, and all advertising the same exact networks, the routers learning the networks would use/believe the EIGRP first (because of the lowest Administrative Distance (AD) of 90. If EIGRP was removed, OSPF at 110 would be believed, and if it was gone, then RIP at AD 120.

Longer matches, (than 23.0.0.0/8) will be routed correctly when those routes are present. Pinging the inside NAT address as a test is great, as the router interface will likely be up. Of course you would need a route to that 23.0.0.0 network from the computer you are pinging from.

With CBT Nuggets, we have the following titles that I have made: Network+, CCNA Security, Firewall, VPN, GNS3 and IPv6 is being worked on right now. CCNA Route/Switch is done by Jeremy, but it is really good as well.

CBT Nuggets offers the Network+ series I created. There is a CCNP offering at CBT Nuggets which is really good too. You can get the details at the CBT Nuggets web site. Thanks, Keith.

Good stuff Keith! I came across your vids while looking for some good video's to send to a friend that is working toward his CCNA. Perfect!

This gentleman is great, thank you for sharing your knowledge.

Very informative and certainly increased my troubleshooting skills. Thanks

Do you have to advertise internal IP network in order for NAT to work? My understanding is that the purpose of NAT is to hide internal IP network so why would you add it to OSPF list of network to be advertise to outside networks.

I can't wait to become a CCIE I love networking so cool thanks again for some of your video's I've seen helped alot. But I'm just confused a couple of things here which I mentioned thanks.

Fantastic lesson !

Hi Keith, How are you? Nice Video this video got my concepts cleared of troubleshooting OSPF I am doing my CCNA and I have learned about RIPV1, 2, OSPF and EIGRP so far haven't learned about NAT yet but this will be taught in my next class thanks alot you are the best. I am so like boosted to go do my CCNA and I am studying like crazy right now. I just want know what is the best Protocol to use now to connect to tons of Networks cause I'm alittle confused with OSPF and EIGRP.

Thanks Keith great video.

Thanks a lot. My ospf didn't work after customizing Nat protocol and static route helps with this problem)))

Great stuff (especially redistribution trick). But why simply not configure NAT on R2?

Thanks alot for the help Keith you guys are great. Where can I get your video's from I want to purchase them. I have the CCNA video's the ICND1 and ICND2 but not CCNP. I also don't have Network+.

I replied to the other couple questions. You can also open a discussion with me on my Facebook page at "Keith Barker Networking". Thanks, Keith Barker

Thank you! You did an amazingly and crazy good video!

Thanks Keith for another great video! So I understand the reason for sending your static route 23.0.0.0 to null0 and then redistributing it. My question is, if I wanted to ping the 23.0.0.0 network, all my pings would be routed to null0. Is there another way to test NAT is working properly, or should I just ping the inside NAT address?

Ok so if you want to connect to a large network you would use BGP and you said EGP is the same as BGP but you would use BGP more? For the service providers EIGRP, OSPF are better to use then, but you can use other protocols depends what the service providers want right?

Very useful video.

Thanks alot keith I want to ask how much your videos are for CCNA and CCNP I would like to watch them and where can get them?

Great!, Thank you

Hey keith , lets assume R2 router is the ISP router and they are not running OSPF routing protocol, on the contrary, R1 as our HQ router here we are running ospf then do we use the same steps?

Why do you setup the static route as: ip route 23.0.0.0 255.255.255.224 null0 instead of: ip route 23.0.0.0 255.255.255.224 fa0/0 You describe Null0 as the packet bin so why does it forward the ICMP packets on successfully?

Static routing you can only connect like 2 routers and 2 pc's together right? but then when you add RIPv1 or v2 to connect the 3rd router and pc which are together it learns from the router 1 and router 2 and pc 1 and pc 2 right? Then OSPF and EIGRP you can connect to any thing except OSPF is connected in groups right and EIGRP can connect to any network when you ping you can ping from anywhere. Plus EIGRP has a Administrative distance of 90 and OSPF has 110.Which makes I think OSPF better Rite?

Thanks a lot!!!

how do you get the interface labels to show?

Is there a way to configure dynamic nat at router 2 while still able to access ftp on pc 1?

@Keith6783 oh thank you... that helps allot!

thank you,, it's help me out....?

gud

hello good evening mr keith please i want you to answer this question if i have this address 10.70.0.0 i know it s a private address which masque will BE compatible with 2000 hoste i was not able to find just because i found 2024 hoste for 255.255.255.224